1. Field of the Invention
This invention relates to a semiconductor device including a nonvolatile semiconductor memory.
2. Description of the Related Art
A nonvolatile semiconductor memory is one of the semiconductor memory devices. Recently, there have been strong demands for the nonvolatile semiconductor memory as a data storage device. Typical nonvolatile semiconductor memories are NOR type flash memory and NAND type flash memory.
To increase the storage capacity of the flash memories, the miniaturization of device elements is in progress. Especially, as the NAND type flash memories have advantages in miniaturization, their storage capacity is being made larger.
A NAND type flash memory comprises a memory cell array area and a peripheral circuit area provided around the memory cell array area (Jpn. Pat. Appln. KOKAI Publication No. 11-31799). The memory cell array area comprises a relatively simple and periodic line-and-space pattern (L & S pattern). The L & S pattern is suitable for miniaturization. Therefore, enhancing the ability of an exposure apparatus makes it possible to form a memory cell array area including dense and large-capacity memory cells. On the other side, as the peripheral circuit area is generally made of irregular patterns, it is not suitable for miniaturization.
In the current process of NAND type flash memory, when the memory cell array area and the peripheral circuit area are exposed at the same time, the miniaturization of the patterns in the memory cell array area is limited by pattern forming capability of the peripheral circuit area.